Laura Wellesley, co-author of the report, said difficulties at any of these critical points could compound already fragile supply chains.

“We are talking about a huge share of global supply that could be delayed or stopped for a significant period of time,” she said.

“A serious interruption at one or more of these chokepoints could conceivably lead to supply shortfalls and price spikes, with systemic consequences that could reach beyond food markets.”

More than half of the globe’s staple crop exports—wheat, maize, rice and soybean—have to travel along inland routes to a small number of key ports in the US, Brazil and the Black Sea, while more than half of these crops transit through at least one of the maritime chokepoints identified.

Wellesley added infrastructure at these junctures was often old and ill-suited to cope with natural disasters, which are expected to increase in frequency as the planet warms.

“What is concerning is that, with climate change, we are very likely to see one or more of these chokepoint disruptions coincide with a harvest failure, and that’s when things start to get serious.”

The report said almost all of the chokepoints identified had already experienced disruptions, including US inland waterways and railways carrying 30% of the world’s maize and soy halted by flooding in 2016, and heavy rain in Brazil, which left 3,000 trucks stranded earlier this year.

The Panama Canal has been regularly hampered by drought, while the Suez Canal has been closed by sandstorms and threatened by attempted terrorist bomb attacks.

The Middle East and North Africa was identified as particularly vulnerable because of its high dependency on food imports and the fact it is encircled by maritime bottlenecks.

Just over a third of all grain imports to the region pass through at least one maritime chokepoint for which there is no viable alternative, the report said.

“The risk of disruption, given the political situation in the region, is high,” it said.

Wellesley said governments needed to diversify production and inventories and invest in climate-resilient infrastructure.

“There have been constant and repeated disruptions at these critical chokepoints over the last 15 years,” she said.

“That none of these events has led to a crisis does not mean that the risk can be discounted.”